Zach Galifianakis is one of those comics whose genius does not quite fit on the big screen. He excels, for example, in the YouTube broadcast of his mock-celebrity-interview spot, "Between Two Ferns." In the segment with Jon Hamm as a guest, the way he says "Mad Men" might be the funniest thing I've seen all year. But when it comes to movies, with the possible exception of G-Force, his full potential has never been realized.

In Dinner for Schmucks, he pretty much steals every scene he's in with Steve Carell. Too bad there aren't more. And in The Hangover, his sad, weird, hilarious future brother-in-law adds an antic element that's not fully exploited — except perhaps in the infamous closing-credit montage of photos, in which he appears to be getting a blowjob from an older woman in an elevator.

In his latest, Anna Boden & Ryan Fleck's It's Kind of a Funny Story, he plays a mental patient who befriends a teenager with suicidal tendencies. Such laughs! Here's what he had to say while promoting the new movie at the Toronto International Film Festival.

What was going on in that elevator inThe Hangover?
The elevator thing was not real. I had a talk with the elderly lady, and I was like, "Ma'am, I'm so sorry we have to do this." She was like an old porno lady. She could care less; she's done much, much worse, as you can see on the internet.

So that wasn't your idea?
No. I actually offered [director] Todd Phillips's assistant $1000 to somehow talk Todd out of having that in there.

The role inFunny Story is relatively serious. Is that what appealed to you?
Yes. After The Hangover, I wanted to make sure that the next thing I did wasn't exactly in the same heartbeat as that. So it was a conscious thing. Plus, those directors are great directors, and I'd seen their movies, and I was very flattered that they would ask someone like me, who's probably known for more-outlandish stuff, to be in the movie. Really, for me, as far as trying to do a movie, it's all about the director — or in this case, directors. And if you feel confident with them, and they let you do your thing, I'm all for it. Even if it's a porno.

Actually, your character inThe Hangover could end up in the same situation as your character here.
Maybe so. I'm playing these parts of nutjobs. But in this one, I was trying to make him a bit more of a thoughtful nutjob.

They say that comedy is a way of counteracting mental pain or sadness or anger. Do you think that's true?
I think that's a stereotype of comics in general, and there's a reason there's a stereotype. Certainly a lot of comics come from bad upbringings and sad situations. I know a lot of comics that are medicated — a lot. A couple of my good friends are overly medicated. Some people are born with a mathematical mind. I think some people are born with a comedic mind. And sometimes it's a combination of both.